The ministry said the US has exported more than 50 per cent of its sorghum crop since 2013.

China's move to self-initiate a dumping investigation rather than by request from industry comes after the Trump administration launched its own self-initiated trade case against Chinese aluminium sheet imports last year, the first such case by the US in over a quarter century.

China said it did not need to receive a request to investigate dumping in "special circumstances" with ample evidence.